scholarly journals ERRATUM: Minimal net incision of the northern Sierra Nevada (California, USA) since the Eocene–early Oligocene

Geology ◽  
2020 ◽  
Author(s):  
Emmanuel J. Gabet ◽  
Daniel P. Miggins
Keyword(s):  
Sierra Nevada ◽  
Early Oligocene

In the caption of Figure 1, panel D, the longitude is incorrect. The correct longitude is 120.1058°W. See PDF file for details.

Minimal net incision of the northern Sierra Nevada (California, USA) since the Eocene–early Oligocene

Geology ◽  
2020 ◽  
Vol 48 (10) ◽  
pp. 1023-1027
Author(s):  
Emmanuel J. Gabet ◽  
Daniel P. Miggins
Keyword(s):  
Sierra Nevada ◽  
North American ◽  
Past Century ◽  
Mountain Range ◽  
Late Cenozoic ◽  
North American Cordillera ◽  
The Past ◽  
The North ◽  
Early Oligocene ◽  
Northern Half

Abstract Significant late Cenozoic uplift (>1000 m) of the northern half of the Sierra Nevada (California, USA), a mountain range in the North American Cordillera, has been a dominant paradigm over the past century. This paradigm has been supported by evidence suggesting that in response to this recent uplift, the range’s deep canyons were incised in the past 3–4 m.y. However, paleochannel elevations compiled from a mining report and geological maps demonstrate that while some modern rivers have incised 560 m below their Eocene–early Oligocene riverbeds, incision by others has been <300 m. For example, Eocene–early Oligocene fluvial gravels can be found just 161 m above the modern channel deep within the canyon of the South Fork American River. We conclude that the initiation of late Cenozoic incision was due to a resumption of a period of downcutting that was interrupted in the Eocene when the rivers were buried by fluvial sediment and by later volcanic deposits. This interpretation challenges the hypothesis that recent uplift was responsible for deep canyon incision. Correctly identifying the causes of recent incision in the northern Sierra Nevada has important implications for understanding the geological history of the North American Cordillera because the range is hypothesized to have been the western ramp of the Nevadaplano.

Middle Eocene through Early Miocene North American Vegetational History: 50-16.3 Ma

1999 ◽  
Author(s):  
Alan Graham
Keyword(s):  
Sierra Nevada ◽  
Rocky Mountains ◽  
Middle Eocene ◽  
Co2 Concentration ◽  
Late Eocene ◽  
Early Miocene ◽  
Northern Rocky Mountains ◽  
Atmospheric Circulation Patterns ◽  
Early Oligocene ◽  
Latest Eocene

During the Middle Eocene through the Early Miocene, erosion of the Appalachian Mountains exceeded uplift and there was a net reduction in elevation. In the Rocky Mountains uplift continued through the Middle Eocene (end of the Laramide orogeny), waned in the Middle Tertiary, and then increased beginning at about 10 Ma. Earlier reconstructions placed paleoelevations in the Rocky Mountains during the Middle Eocene through the Early Miocene at approximately half the present relief. The maximum elevation in the Front Ranges during the latest Eocene was estimated at ~2500 m (~8000 ft; MacGinitie, 1953). Recent approximations are for nearly modern elevations in several areas by the Eocene-Oligocene. Extensive Eocene volcanism deposited ash and blocked drainage systems, augmenting uplift and facilitating the preservation of extensive fossil floras and faunas. In the far west the beginning of Tertiary volcanism in the Sierra Nevada is dated at ~ 33 Ma near the Eocene-Oligocene boundary. A drying trend becomes evident in the Middle Eocene and reduced moisture, along with the waning of volcanic activity in the Oligocene, restricted conditions favorable to fossilization. The number of Oligocene floras in the northern Rocky Mountains is considerably fewer than in younger deposits to the west. In the absence of extensive plate reorganization and orogeny, CO2 concentration decreased, which contributed to a temperature decline that continued through the Cenozoic and intensified in the Late Tertiary. Recall from Chapter 2 (sections on orogeny and volcanism) that uplift plays a role in determining long-term climate by creating rainshadows, altering atmospheric circulation patterns, and increasing the erosion of silicate rocks that causes a drawdown of CO2. This allows heat to escape from the troposphere and results in lower temperatures. Marine benthic temperatures were ~10°C in the early Late Eocene and ~2°C near the Eocene-Oligocene boundary, assuming an essentially ice-free Earth during that time, and increased to ~5-6°Cnear the end of the Early Miocene. Temperatures over land in the midnorthern latitudes are estimated to have dropped by ~12°C between the Late Eocene and Early Oligocene (Wolfe, 1992a).

Geología de la transecta 8: El Palmar-cerro Corea. Sierra Nevada de Santa Marta

2008 ◽  
pp. 25-40
Author(s):  
Elizabeth Cortés Castillo ◽  
Julián Andrés López Isaza
Keyword(s):  
Sierra Nevada

Variedades de durazno (Prunus persica L.) intercaladas en el sistema milpa en la sierra nevada de Puebla, México

2019 ◽  
Vol 12 (9) ◽  
Author(s):  
Ernesto Hernández-Romero ◽  
Reyna Rojano-Hernández ◽  
Ricardo Mendoza-Robles ◽  
José. I. Cortés- Flores ◽  
Antonio N. Turrent-Fernández
Keyword(s):  
Sierra Nevada ◽  
Prunus Persica ◽  
El Sistema

En la Sierra Nevada de Puebla, México, los huertos de durazno (Prunus persica L.) presentan problemas de producción relacionados con alta incidencia de plagas (incluye enfermedades), nutrición deficiente e inadecuado manejo de poda, que acentúan el problema de floración precoz en la mayoría de las variedades mejoradas.

Transportation and the Environment

2017 ◽  
Vol 94 (3) ◽  
pp. 37-61
Author(s):  
Douglas R. Littlefield
Keyword(s):  
Nineteenth Century ◽  
San Francisco ◽  
Sierra Nevada ◽  
Mississippi River ◽  
San Joaquin Valley ◽  
Eastern United States ◽  
Major Health ◽  
San Joaquin River ◽  
Natural Wetlands ◽  
Prevailing View

Some histories of California describe nineteenth-century efforts to reclaim the extensive swamplands and shallow lakes in the southern part of California's San Joaquin Valley – then the largest natural wetlands habitat west of the Mississippi River – as a herculean venture to tame a boggy wilderness and turn the region into an agricultural paradise. Yet an 1850s proposition for draining those marshes and lakes primarily was a scheme to improve the state's transportation. Swampland reclamation was a secondary goal. Transport around the time of statehood in 1850 was severely lacking in California. Only a handful of steamboats plied a few of the state's larger rivers, and compared to the eastern United States, roads and railroads were nearly non-existent. Few of these modes of transportation reached into the isolated San Joaquin Valley. As a result, in 1857 the California legislature granted an exclusive franchise to the Tulare Canal and Land Company (sometimes known as the Montgomery franchise, after two of the firm's founders). The company's purpose was to connect navigable canals from the southern San Joaquin Valley to the San Joaquin River, which entered from the Sierra Nevada about half way up the valley. That stream, in turn, joined with San Francisco Bay, and thus the canals would open the entire San Joaquin Valley to world-wide commerce. In exchange for building the canals, the Montgomery franchise could collect tolls for twenty years and sell half the drained swamplands (the other half was to be sold by the state). Land sales were contingent upon the Montgomery franchise reclaiming the marshes. Wetlands in the mid-nineteenth century were not viewed as they are today as fragile wildlife habitats but instead as impediments to advancing American ideals and homesteads across the continent. Moreover, marshy areas were seen as major health menaces, with the prevailing view being that swampy regions’ air carried infectious diseases.

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